This study aimed to explain principles governing desirable lesson study practice in mathematics in Mazandaran Province’s Educational Office. The research method was qualitative and of phenomenological type. The statistical population of this study included all experts in lesson study. 16 participants were selected through Snowball sampling. The sample size was determined by theoretical saturation. The data collection instrument in this study was semi-structured interview and th validity of the data was assessed and verified by evaluating the participants. The data resulted from interviews were analyzed through categorization method. Totally, 5 major categories were extracted from the interviews, including human aspect (creativity, responsibility and being open to criticism), structural aspect (technological equipment, supervision, programs, load of teacher work, ratio of the number of teacher to the student and applying results), cultural aspect (teamwork, school culture, belief and commitment to impact of lesson study, family cooperation, Researchers' spirit of teacher and principlas, teacher cooperation place of competition), managerial aspect (support, scoring process, authorities’ support, provision of budget, support of other school factors and time) and pedagogical aspect (exchange of useful educational experiences, workshops, new teaching styles, provincial team of lesson study, educational content, conversion of quantitative evaluation to descriptive and educational design).

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